1. Field of the Invention
The present invention relates generally to a lighting system for a vehicle and more specifically to an illuminator for use, in combination with a remote light source, as a headlight or taillight on a vehicle.
2. Description of the Related Art
Conventional vehicle lighting systems typically use a bulb and reflector combination. In a bulb and reflector combination, the filament of the bulb is placed at or near a focal point of a parabolic reflector. The focal point of a reflector is that point at which parallel rays of light meet after being reflected by the reflector. Conversely, light rays emanating from the focal point are reflected as parallel rays of light. The light emitted by the bulb filament is collected by the reflector and reflected outward to form a light beam. A lens is used to shape the light beam into a specified pattern to satisfy vehicle lighting standards and regulations. Typically in an automotive application, a conventional bulb and reflector combination only collects and reflects about thirty percent of the light emitted from the bulb filament.
When used in an automotive application, bulb and reflector combinations have several disadvantages which restrict aerodynamic and aesthetic styling; e.g., the depth of the reflector along its focal axis and the height of the reflector perpendicular to the focal axis have greatly limited attempts at streamlining the front end of a vehicle. Additionally, the thermal energy given off by the bulb filament during operation must be considered. This in turn dictates the size of the reflector and the material which can be used in its construction. Decreasing the size of the reflector requires use of high heat plastics for the lens and body of the reflector.
Another disadvantage of a bulb and reflector combination is that the light not radiated toward the reflector is radiated outward through the lens into a region outside the specified or established beam pattern resulting in glare and an undesirable beam pattern.
One approach to utilize and control the light radiating directly outward from the filament is disclosed in U.S. Pat. No. 4,654,758 which shows a headlight having a paraboloidal shaped reflector with a light emitting element placed at or near the focal point of the reflector. A transparent cover plate or lens seals the reflector. A convex mirror is positioned between the lens and light emitting element to reflect the directly outward radiating light to the paraboloidal reflector to further coverage the light beam and prevent spreading over a wide spatial angle.
While this approach may be useful, a certain portion of the light emitted by the filament escapes reflection. Additionally each light ray must be reflected several times before it exits the reflector. Since each reflective surface is not ideal the rays diffract and lose energy. Finally the disclosed device fails to consider the thermal energy given off by the filament.
Therefore, it is desireable to have a high efficient, low profile illuminator having reduced space requirements as dictated by both thermal concerns and vehicle aerodynamic and styling requirements.